Under the same 'Airtel One' plan, ISD calls to different groups of countries are billed at different per minute rates. A person makes a total of 12 minutes of ISD calls in a month. If 80% of his ISD bill amount came from calls made to the 'Rest of the World' group, then the ISD calls of the minimum duration were made to which of the following groups of countries?

Question

Statement: Company has made it Compulsory to mark online attendance using facial recognition software — Notice in an office.
Assumptions: 1) Notice will be read 2) Online attendance will benefit the company

Answer 1

Try assuming actual numbers and see if the answer changes, that quickly shows whether the data on hand is enough.

USA, Canada, Europe (Fixed Line): if this group is billed at a low per minute rate, it could take up several minutes yet still contribute only a small share of the money, so we cannot rule this in or out as the group with minimum duration.
Gulf, Europe (Mobile), SAARC: the same logic applies here. A cheaper per minute rate could mean this group used very few minutes even if its share of money is decent, or many minutes if the rate is very low.
Rest of the world: holding 80% of the bill amount does not fix the number of minutes used, because if its per minute rate is high, even a short call duration can create 80% of the total bill.

Assume two different rate setups: one where Rest of World is charged much higher per minute, and one where all three groups are billed near equally. In the first setup, Rest of World could use very few minutes and still cause 80% of the bill. In the second setup, Rest of World would need most of the 12 minutes to reach 80% of the bill. Since both setups fit the given facts but lead to opposite answers, the data is not enough to pick one group.

Let's summarize:

The 80% figure describes money, not time.
Per minute rates for each group are never stated.
Two different rate assumptions give two different answers, so the question cannot be settled with the data given.

So the correct choice is that the answer cannot be determined.

Answer 2

Try assuming actual numbers and see if the answer changes, that quickly shows whether the data on hand is enough.

USA, Canada, Europe (Fixed Line): if this group is billed at a low per minute rate, it could take up several minutes yet still contribute only a small share of the money, so we cannot rule this in or out as the group with minimum duration.
Gulf, Europe (Mobile), SAARC: the same logic applies here. A cheaper per minute rate could mean this group used very few minutes even if its share of money is decent, or many minutes if the rate is very low.
Rest of the world: holding 80% of the bill amount does not fix the number of minutes used, because if its per minute rate is high, even a short call duration can create 80% of the total bill.

Assume two different rate setups: one where Rest of World is charged much higher per minute, and one where all three groups are billed near equally. In the first setup, Rest of World could use very few minutes and still cause 80% of the bill. In the second setup, Rest of World would need most of the 12 minutes to reach 80% of the bill. Since both setups fit the given facts but lead to opposite answers, the data is not enough to pick one group.

Let's summarize:

The 80% figure describes money, not time.
Per minute rates for each group are never stated.
Two different rate assumptions give two different answers, so the question cannot be settled with the data given.

So the correct choice is that the answer cannot be determined.

Show Hint

The Correct Option is D

Solution and Explanation

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